1. Field of the Invention
The present invention relates to a method of manufacturing a stamped part having extrusions, and an apparatus for manufacturing the part.
2. Background Art
The use of drawn structural extrusions as a means to reduce the cost of a finished part, particularly a stamped part, is well known. Typically these parts do not have the thickness of material required for the forming of threads, which would allow the part to be bolted directly into place. Attempts to solve this problem include the use of a separate fastener such as a threaded nut, or attaching additional material to the part in the area to be threadedxe2x80x94e.g., using a weld nut. A better alternative is to extrude and thread the part itself, thereby eliminating the cost of the additional components, and the cost of attaching the components.
Despite the overall cost benefit associated with extruding a stamped part, the extruding process itself remains a specialty. A great deal of expertise and experience is required to ensure that the extrusion that is formed is capable of being threaded and is strong enough to meet the customer""s structural requirements. In addition, extruding a stamped component can significantly increase the processing cost. Two separate die assemblies are required: an extrusion die, which forms the extrusions, and a component die, which is used to form the workpiece into the finished part. Typically the extrusion die and the component die are part of the same die assembly. This significantly increases the size of the die assembly, which not only increases the cost of handling the die assembly within the processing facility, but also creates logistical problems and increases costs when the die assembly is transported to or from the customer""s facility. This further limits the number of processing facilities that can perform this type of extrusion work. Not only must the processor have the requisite level of skill, but facilities and equipment capable of handling extremely large die assemblies must also be available.
One method used to overcome some of the problems associated with handling these larger die assemblies is to xe2x80x9csplitxe2x80x9d the die between the extrusion and component portions. This has the advantage of making the die assembly easier to handle and less costly to transport; however, this method has inherent limitations of its own. Specifically, this type of xe2x80x9cdie splittingxe2x80x9d increases the engineering costs associated with the design of the die assembly. Splitting the die makes it necessary to design two portions that can be separately attached to a press, and are capable of being properly aligned with one another once they are installed on the press. Additional costs are then incurred each time the die assembly is attached to the press, since the alignment of the extrusion portion and the component portion is critical. Therefore, neither of the two methodsxe2x80x94using a single, extremely heavy but complete die assembly, or splitting the die and dealing with critical alignment issuesxe2x80x94eliminates the problems inherent in the extrusion process.
Accordingly, it is desirable to provide a method of extruding a stamped part which overcomes the above referenced shortcomings of prior art methods, by reducing the cost of the extrusion process and at the same time eliminating the need to maneuver and transport extremely heavy die assemblies.
The present invention provides a method of manufacturing a stamped part with extrusions, such that the net costs to both the processor and the customer are reduced, and at the same time the ability to maneuver and transport the die assemblies is greatly increased. The present invention also provides for a method of doing business which utilizes the manufacturing method such that sales are increased and costs are lowered. Further provided in the present invention is an apparatus to be used in the manufacturing method.
Specifically, the manufacturing method dedicates a stamping press with a moveable ram and a stationary bolster plate to a particular set of finished parts. Each part in the set has extrusions that are similarly configured. Permanently attached to the ram and bolster plate of the press are upper and lower shoes that are configured to cooperate with replaceable die subassemblies.
The upper and lower shoes are weldments that are assembled prior to being permanently mounted on the stamping press. Each shoe comprises a plurality of nitrogen cylinders mounted between two sub-plates that are welded to a plurality of vertical support members. Once the shoes are assembled, the upper shoe is attached to the movable ram on the press, and the lower shoe is attached to the stationary bolster plate opposite the upper shoe.
An extrusion die sub-assembly is then assembled and configured for use with more than one type of finished part. Use of the extrusion die sub-assembly will result in some of its components, known as perishables, becoming worn and requiring replacement. However, the extrusion die sub-assembly itself is only replaced when the finished part changes significantly, such as when a finished part from a new product line is ordered. In a preferred embodiment, the extrusion die sub-assembly is assembled from components which are, to the extent possible, standard in both size and shape. This significantly reduces the cost of the extrusion die sub-assembly, by allowing the components to be purchased and/or manufactured in bulk quantities.
The method further requires the assembly of a component die subassembly designed to meet the customer""s finished part specifications. The extrusion die sub-assembly is mounted to the upper and lower shoes, and the component die sub-assembly is directly mounted to the ram and bolster plate of the press. The two die sub-assemblies are then mounted in such a way they can be easily removed. Typically, the extrusion die sub-assembly is removed to replace its perishable components, and the component die-subassembly is completely replaced when a new finished part is ordered. A workpiece is fed into the stamping press where it is first extruded into a preform, and then formed into the finished part. The actual processing of the workpiece resembles a standard progressive die stamping process.
The business method utilizes the manufacturing method of the present invention to benefit both the manufacturer and the customer. A standard stamping operation does not utilize upper and lower shoes permanently attached to the press. Rather, only portions of the shoes are used in a standard operation, and these are part of the tooling costs paid for by the customer. Typical tooling costs include the cost of the extrusion die set and the component die set. Each time the customer orders a different finished part, new tooling is purchased. Hence, the cost of at least a portion of the shoes is a reoccurring cost for the customer-one that is often significant. In contrast to a standard operation, the present business method designates the shoes as capital equipment. This means that the stamping facility now bears this cost, but amortizes it over a long period of time. The net cost to the stamping facility is negligible compared to the increase in business resulting from significantly lowering customer tooling costs. As an alternative, the capitalized cost of the shoes can be added into the price charged for a finished part. This additional cost to the customer is minimal, since the same shoes are used for many different finished parts. Moreover, the same shoes can be used for parts made for different customers, further reducing the cost to an individual customer. Either method results in a net cost savings to the customer.
The business method also includes standardizing extrusion configurations in such a way that the needs of most customers are met by using one of the standard configurations. Further, performance and dimensional data for the standard configurations are published and made available to the customers. This allows the customers to have before them all the information they need to make an informed decision regarding the extrusions they choose for their parts. In addition, this allows the stamping facility to assemble standard extrusion die sub-assemblies from standard parts inventoried in bulk. This results in a net savings to both the customer and the stamping facility. Hence, capitalizing the upper and lower shoes, standardizing the extrusion configurations, and following the steps of the manufacturing method, results in a business method which benefits both the manufacturer and the customer.
Accordingly, one aspect of the present invention provides an improved method of manufacturing a customer""s finished part such that costs to both the manufacturer and the customer are reduced.
One aspect of the invention is a method of manufacturing a finished part to a customer""s specifications using a stamping press having upper and lower shoes. The method comprises attaching the upper shoe to a moveable ram of the press, and attaching the lower shoe to a stationary bolster plate of the press, the shoes being configured to cooperate with replaceable die sub-assemblies. An extrusion die sub-assembly is assembled and configured to extrude a workpiece into a preform for the finished part. This die sub-assembly is then replaceably attached to the upper and lower shoes. A component die sub-assembly is assembled based on the customer""s finished part specifications. The component die sub-assembly is then replaceably attached to the ram and bolster plate of the press. Finally, a workpiece is fed into the stamping press where it is progressively formed: first by extruding it into a preform with the extrusion die sub-assembly, then by forming it into the finished part with the component die sub-assembly.
Another aspect of the invention is a method of doing business in a stamping facility whereby net costs are lowered for the stamping facility and its customers. The business method comprises capitalizing an upper shoe attached to a moveable ram of a press, and capable of cooperating with replaceable die subassemblies. Further, a lower shoe attached to a stationary bolster plate opposite the movable ram on press is also capitalized. Capitalizing the shoes removes their cost from the customer tooling by having the stamping facility bear the initial cost. Capitalizing the shoes also includes amortizing their cost over time, such that the cost is spread over many different finished parts. The business method further comprises standardizing extrusion configurations and inventorying a variety of different die components adapted to make the standard configurations. An extrusion die sub-assembly is assembled using at least some of the inventoried components; it is then replaceably attached to the upper and lower shoes. A component die subassembly is assembled based on the customer""s finished part specifications; it is then replaceably attached to the ram and bolster plate of the press. Finally, the customer""s finished part is manufactured by feeding a workpiece into the stamping press where it is first extruded into a preform by the extrusion die sub-assembly, and then formed into the finished part by the component die sub-assembly.
It is another aspect of the present invention to provide a modular progressive stamping die assembly which comprises a stamping press having a moveable ram for imparting a stamping force to a workpiece, and a stationary bolster plate located opposite the moveable ram. An upper shoe is attached to the ram and a lower shoe is attached to the bolster plate. Both shoes are capable of cooperating with replaceable die sub-assemblies. An extrusion die sub-assembly, replaceably attached to the upper and lower shoes, is configured to extrude the workpiece into a preform for a finished part. A component die sub-assembly, replaceably attached to the ram and bolster plate of the press in a position to receive the preform from the extrusion die sub-assembly, is configured to form the preform into at least a near net shape.
The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.